This application is a 371 of PCT/JP01/01162, filed Feb. 19, 2001, published in WO 01/60942 on Aug. 23, 2001.
The present invention relates to fluorescent compounds, more particularly, to fluorescent compounds that emit light of various colors when such energy as electric energy or electromagnetic energy is applied thereto, and that can be used for electroluminescent elements.
Such a color of visible light as blue, yellow green or red, emitted by an electroluminescent element, which we will call xe2x80x9cEL elementxe2x80x9d hereafter, can easily be controlled through an appropriate choice of compounds used for the fluorescent material. Very many compounds have been developed for the fluorescent materials.
These compounds include derivatives of aluminum-8-hydroxyquinolinolate complexes, those of oxadiazoles, those of triazoles, those of di(styryl)arylenes, those of cumarines, those of bis(styryl)amines, etc.
The use of these compounds, however, has involved several problems. One of them is that the production cost is high, because the raw materials are not commonly marketed ones. Another is that their production requires a process of many steps and special reaction conditions. Besides, their yields are small. Therefore only a few of them have been put to practical use. Even for the compounds actually in practical use, a further reduction in production cost is desired.
Also, technically, of the compounds that emit blue light, yellow green light, or red light have been especially desired those that emit light of a clear red. In detail, red light having been used in conventional CRT displays had a wavelength of 625 nm at the maximum. In order to make the red light clearer, it is necessary and desired to employ compounds that emit a light having strong sharp peaks in the wavelength range of 630-700 nm.
Further, from the industrial viewpoint, is also desired the development of such fluorescent materials as can emit light of various and desired wavelengths only through chemical modifications to compounds belonging to the same category. Specifically, intended is the development of fluorescent compounds of which wavelengths of the emitted lights can be changed only by chemically modifying a skeletal structure common to the compounds, for example, by replacing functional groups of the compounds. If compounds emitting the lights of desired wavelengths are obtained by such a simple way, the kinds of raw materials and the steps of the producing processes will dramatically be reduced, compared with the conventional way in which a fluorescent material having a different skeletal structure was produced for each light of an intended wavelength.
This invention was made to overcome the above-mentioned problems. An objective of the invention is to provide new fluorescent compounds that are easily produced at a low cost.
Another objective of the invention is to provide fluorescent compounds that have the same basic skeletal structure and emit lights of desired different wavelengths by choosing functional groups bonded to the skeletal structure.
Still another objective of the invention is to provide a new compound emitting red light of which wavelength is 630-640 at the maximum.
The invention to achieve the objectives provides fluorescent compounds shown by general formula (1):
Axe2x80x94Arxe2x80x94Bxe2x80x83xe2x80x83(1)
wherein Ar is an aromatic skeleton shown by general formula (2a) or (2b), A is an electron donating group, and B is an electron attractive group. 
In particular, electron donating group A with which the group or atom at the 2-position of naphthalene is replaced, is, for example, an alkylamino group, amino group, an aminoaryl group, an alkylaminoaryl group, an alkoxy group, an alkoxyaryl group, an arylalkoxy group, an alkyl group, an aryl group or a halogenated alkyl group. The alkylamino group, alkylaminoaryl group, the alkoxy group, the alkoxy moiety of the alkoxyaryl group, the alkoxy moiety of the arylalkoxy group, the alkyl group and the halogenated alkoxy group each have 1-20 carbon atoms. For the alkylamino group are used monoalkylamino groups and dialkylamino groups. The electron attractive group is an electron attractive ethenyl group or aldehyde group.